The present invention relates generally to a method and apparatus for measuring the concentration of a compound in a liquid medium in which the medium being examined is passed through an enzyme bed or the like for the transformation of the compound into a converted reaction product, the concentration of which can then be easily measured in a measuring unit. The enzyme bed can either serve to form a converted reaction product which is then measured after being conducted from the reaction chamber or can serve to remove the reaction product therefrom, the absence of which is then measured by the measuring unit. In particular, the method and apparatus of the present invention are particularly useful for measuring the content of a low molecular weight compound, such as for example glucose in a complex medium such as for example blood.
In measuring the concentration of a low molecular weight compound in a complex medium, such as for example blood, a dialyzer is employed in contact with the complex medium and through which dialysis fluid is conducted to receive by diffusion a portion of the low molecular weight compound to produce a dialysate. This dialysate is then transmitted to a reaction chamber comprised of an enzyme bed or the like which serves to promote the conversion of the low molecular weight compound into a converted reaction product and then to a measuring unit for measuring the content of a converted reaction product in the fluid conducted from the reaction chamber. This measurement of the concentration of the converted reaction product is representative of the concentration of the low molecular weight compound in the complex medium. Such a measurement can, in turn, be used for controlling the treatment of the complex medium, for example, by supplying insulin and/or glucose to the blood of the patient being examined.
However, during such a process, there is a possibility that gaseous products carried by the dialysate may adversely affect the enzymes in the reaction chamber, the conversion of the low molecular weight compound into the converted reaction product and/or the measurement of the content of the converted reaction product. For example, the pentration of air into the enzyme bed may adversely affect the accuracy of the measurement of the concentration of the low molecular weight compound in the complex medium which is particularly disadvantageous where such measurement is being used to control the supply of insulin and/or glucose to a patient under examination.
Accordingly, it is an object of the present invention to provide a method and apparatus for overcoming these disadvantages of the prior art. Specifically, it is an object of the present invention to provide a method and apparatus for obtaining a reliable measurement of the concentration of a compound in a liquid medium, and in particular, for obtaining the measurement of a concentration of the low molecular weight compound in a complex medium.